Chapter 13 - Southern Ocean

Abstract

This chapter provides an overview of the Southern Ocean. The “Southern Ocean” is the broad ocean region surrounding Antarctica. It is not a formal geographic region in the sense of the Pacific, Atlantic, or Indian Oceans or the many marginal seas, as it is not surrounded by continental land masses. However, the concept of a Southern Ocean is important because the latitude range of the Drake Passage between South America and the Antarctic Peninsula has no north–south boundaries (except in the deep water). As a result, the strong Antarctic Circumpolar Current (ACC) flows continuously eastward, encircling Antarctica without wrapping back to the west; it dominates the Southern Ocean's large-scale circulation. There is no western boundary at the Drake Passage latitudes to support western boundary currents and wind-driven gyres in the upper ocean, although deep topography does provide barriers for western boundary currents in the deep and abyssal waters. The ACC is ocean's closest analog to the major wind systems, the westerlies and easterlies, because the atmosphere also has no boundaries. The chapter describes Southern Ocean fronts and zones. It explains Antarctic circumpolar current, Weddell and Ross Sea gyres, and mid-depth to bottom circulation. A discussion on Antarctic intermediate water and circumpolar deep water is also presented in the chapter.